Visual inspection of railway wagons

High Level Software Innovation Measurement technology Public Safety

Is the block brake worn? How thick is the pantograph contact strip? Is an incorrectly fitted screw coupling hanging down? In future, SBB's "Visual Inspection System" (VIS) will use cameras to monitor passing trains. Vehicle owners and railway companies can install their own algorithms on the platform to analyse the images.

  • Initial situation

    Rail vehicles for goods and passengers require regular maintenance. But how often? Short intervals are expensive. Waiting too long, on the other hand, increases the risk of an accident.

  • SCS solution

    The "Visual Inspection System" (VIS) uses cameras to monitor passing trains. Railway companies, vehicle owners and infrastructure managers can analyse the images of their vehicles using their own algorithms.

  • Added value

    The "Wayside Intelligence" (WIN) platform provides operators with the condition of their vehicles or the calculated values from the algorithms. This allows them to plan maintenance and maintain a high level of safety - despite longer intervals.

Project insights

Today, around 250 measuring systems already check trains travelling on the Swiss rail network: they check whether brakes or axles are overheating, a wheel is running out of true, the load of a wagon has slipped or the cover plates and antennas of lorries are violating the clearance gauge. If a hazard is detected, the train control unit alerts the control centre and the train is immediately stopped, slowed down or routed to an intervention track at the next station. The train control systems have been continuously expanded since 2008 and supplemented, for example, with natural hazard alarm systems that stop train operations in the event of rockfalls and avalanches.

The next step is now to monitor the trains with cameras. Modern image processing algorithms are able to detect many types of damage and hazards. A typical example is the screw couplings used to couple freight wagons or older passenger carriages. As each wagon has a screw coupling on each side, one remains unused. This must be correctly suspended, otherwise it dangles down, can hit the ground and destroy railway infrastructure. Today, dedicated detectors are only used for dangling parts. In future, cameras will record various things at the same time, such as the thickness of the contact strip on the pantograph, the wear on the block brakes or the remaining mileage of a wheel. This not only detects hazards, but also makes it easier to plan wagon maintenance.

Suspended screw clutch
Suspended screw coupling

However, the system cannot send all images to every vehicle owner and every railway company that runs trains on the SBB infrastructure. The data volumes would be too large. The WIN platform is therefore designed in such a way that fast computers in the immediate vicinity of the cameras analyse the images and only send the results (the values from the algorithms) to the customers of SBB Infrastructure Ltd. Of course, images can also be used in the event of a conspicuous value. These are stored on the computers on site.

Rail transport companies and vehicle owners can install their own image processing algorithms on the WIN platform. The system recognises who the vehicle owner is via an RFID tag on the vehicle. The images are then analysed by the algorithms and the results are sent to the authorised users via a machine-readable interface – usually the deviation from the standard value. The companies can use this data to plan maintenance. SBB Infrastructure customers therefore decide what they want to measure and when they want to take action.

The existing measuring systems of the train control equipment are also integrated into the WIN platform. For example, weight measurement on the track: if a wheel has blocked for some reason, there may be a flat spot because it has slipped on the rail. This spot now hits the track with every revolution. Weight sensors on the track (several strain gauges on the rail over a short distance) recognise when the weight does not pass evenly. The wheel may even be in the air for a short time, only to hit the rail all the harder afterwards. A dynamic coefficient is calculated from these weight values and sent to the authorised users.

The WIN platform is already operational today and is being successively expanded with additional functions. The first camera measuring points have been installed and algorithms are being integrated.

Weight measurement on the track when a wheel passes through that has a flat spot. The strain gauges are distributed over a certain length. The dynamic force is highest where the end of the flat spot meets the rail.

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